1. Field of the Invention
This invention relates to a new expansion device for a refrigeration system and to a new piston for such an expansion device as well as to new methods of making such an expansion device and such a piston.
2. Prior Art Statement
It is known to provide an expansion device for a refrigeration system and comprising a housing means having opposed port means for coupling the device in the system and being separated from each other by an internal valve seat means of the housing means, and a movable piston disposed in the housing means and having a first end surface means adapted to engage against the valve seat means to tend to close the same when the piston is disposed in a first position thereof in the housing means, the housing means having an annular shoulder means, the piston having a second end surface means for engaging against the shoulder means when the piston is disposed in a second position thereof in the housing means, the piston having a passage means passing therethrough and through the end surface means thereof for interconnecting the opposed port means together in a restricted manner when the piston is in the first position thereof, the piston having an outer peripheral surface means interconnecting the end surface means together and being provided with a plurality of grooves therein for interconnecting the opposed port means together in a substantially nonrestricted manner when the piston is in the second position thereof. For example, see the Duell et al U.S. Pat. No. 3,992,898.
Also, see the Lovingham U.S. Pat. No. 3,805,825 wherein it appears that the movable piston check valve means thereof comprises a one-piece member formed of polymeric material.
Also see the Genbauffe U.S. Pat. No. 4,431,117, wherein a hermispherical end is disposed in a self-aligning manner into a frusto-concial seat.